With the tv showing heart rending eyewitnesses reports in the background, I feel the need to report on my progress of the Ubuntu installation on my dad's desktop. The first results are very, very promising. Ubuntu feels a lot faster and has a lot less trouble with many things. For example, Hanneke (my dad's girlfriend) had trouble with certain email in Evolution. They would lock the program and crash it. Under Mandriva, that is. With Ubuntu, she uses almost the same Evolution and has no trouble at all.
I did have to install some programs for my father to use, like KMail, which aren't usually installed under Ubuntu, but I wasn't able to import his KMail-tree into Evolution, so I saw no other solution for it. Well, switching to IMAP one of these days would be a really good thing. Also, I had to tweak the KMail config file (~/.kde/share/config/kmailrc) a bit to point to the directory Mandriva uses for email under KMail, which is ~/.Mail instead of Ubuntu's default ~/.kde/share/something/more/here. That was easy to find out, but I can imagine people having difficulty with that switch.
All in all, I think they're very happy with the result so far. I'm considering switchin to the development branche of ubuntu on thei machine, though. Some things could be a bit better imnsho.